It’s fortunate that summer is over; this volume is not the best beach reading. Of course, that’s true of many excellent books that require careful attention, a comfortable chair, a hot mug of tea and sufficient solitude to do justice to the rich material packed within their pages.

In “America’s Unwritten Constitution,” Akhil Reed Amar aims high and has produced a masterful, readable book that constitutes one of the best, most creative treatments of the U.S. Constitution in decades. A professor of law and political science at Yale, Amar is no stranger to this territory. His past writing credits include “America’s Constitution: A Biography,” which illuminates the text of the nation’s most revered document. Now he tackles a more daunting assignment: mapping out the unwritten aspects of our nation’s fundamental charter — a task akin to catching the reflection of a mirror. Perhaps better than other any modern-day writer, though, he succeeds in showing how other, less conspicuous sources combine with the written text to hold the Constitution together like a woven fabric.

A warning: The book is not for the faint-hearted. At 485 pages of text, it presupposes a keen interest in history, government, politics and law. Yet it is filled with thought-provoking material and fun vignettes, suitable for a wide audience.

Amar opens with a lost episode in American history: Senators are battling during the impeachment trial of President Andrew Johnson in March 1868, debating whether Sen.Benjamin Franklin Wade of Ohio is eligible to vote. As president pro tem of the Senate, Wade is next in line to succeed Johnson if the president is convicted. (The vice presidency is still vacant after Lincoln’s assassination.) Some senators claim it will be “an intolerable conflict of interest” if Wade — who will directly benefit if Johnson is ousted — casts a vote. Yet the text of the Constitution is silent on the matter. Other senators retort that making Wade recuse himself will strip Ohio of one of its two precious votes on this crucial impeachment question.

In the end, the Senate follows history, precedent and a broad view of the Constitution to allow Wade to vote. Not surprisingly, he casts a “guilty” ballot. Yet Johnson escapes conviction by a hair, and the integrity of the Constitution is preserved. Thanks to a recognition that a crabbed reading of the text does not always produce a result that’s consistent with the Constitution as a whole, the spirit of the nation’s fundamental charter remains intact.

Writing the unwritten. (George Bates for The Washington Post)

Similarly, Amar paints a vivid picture of the women’s suffrage revolution that culminated in the passage of the 19th Amendment in 1920, giving female citizens the right to vote. He invokes this history — and the admonitions of Abigail Adams and Eleanor Roosevelt — to argue that Congress holds unusually broad power to enact laws that protect women’s rights in a variety of areas. This is true, he says, “for the simple reason that the unwritten Constitution is a Constitution of American popular sovereignty” that must be viewed through the lens of the adoption of the 19th Amendment.

Such sparkling stories illustrate that the Constitution needs to be read “as a whole rather than as a jumble of discrete clauses.” The unwritten commands of America’s Constitution, Amar declares, exist side by side with the written text, and “the two stand together and support each other.”

But he bristles at the notion that the unwritten Constitution is nothing but an invention of activist judges who make up rights out of whole cloth to satisfy their personal predilections. Rather, it comes from viewing the written document as a whole (including its amendments), instead of parsing words and reading them in lifeless isolation. It comes from the Federalist Papers and other founding documents. It comes from historical context. (President George Washington’s diplomatic efforts culminating in the Jay Treaty set the stage for President Thomas Jefferson’s broad authority in negotiating the Louisiana Purchase, which shaped the scope of presidential power today.) It comes from the Declaration of Independence, Lincoln’s Gettysburg Address and other iconic texts that help define what “we the people” stand for as a nation. (For instance, President John Kennedy openly invoked the Gettysburg Address in June 1963, in calling on Congress to enact comprehensive civil rights legislation to give meaning to the equal protection clause of the 14th Amendment.)

Amar’s approach is refreshing. He doesn’t place all his eggs in the basket of “original intent” and “strict constructionism” favored by today’s conservative legal thinkers. Nor does he rely on a touchy-feely notion of a “living Constitution” that is embraced by liberal jurists who are criticized as ideologues.

Indeed, Amar decries today’s bipolar political culture, declaring, “Too often, each side shouts past the other, and both sides overlook various ways in which the text itself, when properly approached, invites recourse to certain nontextual — unwritten — principles.”

This book is constructed like a towering Jenga game. It presents constitutional brain twisters such as: Could a president be arrested while traveling in a state hostile to his policies and thrown in jail for alleged criminal conduct, even though this might cripple the nation? The Constitution tells us nothing about whether presidents can be indicted or incarcerated while in office. (The answer is: probably not. You’ll have to read the book to see why.)

The book includes surprise discoveries such as that the version of the Constitution most often used in schools and courts — hand-signed by the framers — is not the “official” version of the document as ratified and printed on Sept. 28, 1787. Some words and punctuation do not even match. As Amar quips, so much for “hardcore” textualism.

The book includes thought-provoking chapters such as “Remembering the Ladies: America’s Feminist Constitution,” which explains why the ratification of the 19th Amendment in 1920, granting women the right to vote, empowers Congress to protect women’s rights in a host of modern contexts.

Perhaps the most intriguing chapter is the last, in which Amar visualizes America’s Constitution in the future. According to him, we might see:

●A system by which Americans could pick presidents by direct national popular election by 2020;

●A U.S. Senate that more directly reflects population, perhaps with up to eight senators for large states;

●Term limits for legislators, recall elections and line-item vetoes, as exist in many states.

Amar makes a creative case that America’s written Constitution and its unwritten Constitution, since the beginning of the nation, have fit snugly together to form a single, more perfect union. He reminds us that “ordinary citizens celebrate this document — at times to the point of idolatry, revering it without reading it.” A good starting point is to read the Constitution. A next worthwhile step is to brew a perfect mug of tea, find a quiet chair and read Amar’s book.

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